U.S. Pat. No. 3,392,159 discloses that alkenes can be suspension polymerized at temperatures of 100.degree. C. or less in the presence of a catalyst which is prepared by adding an organo-magnesium compound to a titanium compound and, optionally, subsequently adding an organo-aluminum compound to the mixture of the magnesium and the titanium compounds. The organo-magnesium compound which is used in the process of this patent is obtained as a reaction mixture, having a solid phase and a liquid phase. The patent discloses that both of these two phases are preferably added to the titanium compound, in view of the polymerization efficiency and the resulting polymer properties. The reaction between the organo-magnesium compound and the titanium compound normally produces a reaction mixture which consists of a blackish precipitate which is finely distributed in a liquid phase.
French Pat. No. 2,016,081 discloses that alkenes can be polymerized at reaction temperatures of 20.degree.-150.degree. C., preferably 50.degree.-100.degree. C., in the presence of a special type of supported catalyst. The active catalyst component consists of a hydrocarbon-insoluble reaction product of a titanium compound and a magnesium alcoholate, to which reaction product an organo-aluminum compound has been added. Unconverted titanium compound is washed out of the catalyst with hydrocarbons. Prior to the reaction with the titanium compound, the magnesium alcoholate may be reacted with other inert solid substances, like various halogenides, sulphates, carbonates and the like, e.g. McCl.sub.2, BaCO.sub.3, etc.
U.S. Pat. No. 3,453,346 discloses that block copolymers can be prepared from .alpha.-olefins, and vinyl halides or vinylidene halides in the presence of solid polymerization catalysts which consist of a mixture of a halide of a transition metal of Groups IV-VI of the Periodic System such as TiCl.sub.4, TiCl.sub.3 or TiCl.sub.2, and an organo metallic compound of an element of Group I-A or II, or an aluminum compound. Lithium compounds are preferred. The patent discloses that a third catalyst component may optionally be added to increase stereospecificity. The third catalyst component may be an alkali halide, magnesium oxide, aromatic ethers, hydrides of sodium, potassium, lithium, calcium, magnesium, barium, strontium, aluminum, titanium, or zinc.
Co-pending U.S. patent application Ser. No. 824,996, filed May 15, 1969, discloses the process for polymerizing alkenes in the presence of a catalyst comprising a mixture of an organo-aluminum halide, a titanium compound and an organo-magnesium compound, to which mixture an activator is added. The activator is an oxyhydrocarbon such as an alcohol, acid, ester, aldehyde or ketone.
All of the catalyst systems disclosed in the above identified patents and patent applications are either prepared from mono- or dihydrocarbylmagnesium, or contain solid components dispersed in a liquid vehicle. Mono- or dihydrocarbylmagnesium compounds are inflammable, and are also susceptible to the action of moisture and oxygen. Special precautions are therefore required for the use of such compounds.
Special precautions are also required when catalysts are used which contain solid components, such as supported catalysts, otherwise such catalysts may give rise to substantial process difficulties. For instance, a suspension of such a solid catalyst will settle if it is not sufficiently agitated, and there is a substantial danger of catalyst accumulation in the reactor. It is rather difficult to maintain a homogeneous distribution of suspended catalysts in a suspension vehicle, and non-uniform polymer product may be obtained.
French Pat. No. 1,169,039 discloses that alkenes, and many other polymerizable compounds, can be polymerized in the presence of a catalyst system which may be a titanium halide and an organo-metal compound, to which aluminum alcoholate, for instance, is added. The patent discloses that alcoholates of 14 other metals, including magnesium, may be added, but that sodium propoxide, calcium phenoxide, and aluminum ethoxide are preferred. The patent is directed toward obtaining polymers having higher molecular weights. As illustrated in the working example of this patent, the catalyst activity is lowered by the addition of the metal alcoholate.